The present invention relates to a method of detecting a train in a block section using a track circuit, and particularly to a train detecting method which is capable of maintaining safety even in the event of a failure in a signal transmission path of the track circuit.
A conventional railway system employs a method which uses a track as part of a signal transmission path to detect the existence of a train in a block section. In such a method, the track is electrically divided into plural sections, each having a predetermined length. Such a section forms a part of an electric circuit, which is commonly referred to as a track circuit. At respective ends of each track circuit, there are arranged transmitter/receiver devices, one of which transmits a signal for detecting a train continuously or at a constant time interval and the other of which receives the transmitted signal.
If a train does not exist in the section formed by a track circuit, a signal transmitted by a unit on the transmitting side is able to reach the unit on the receiving side. If, however, a train exists in the section formed by the track circuit, a signal transmitted by a unit on the transmitting side does not reach the unit on the receiving side, because the pair of rails which form the track circuit are short-circuited by the wheels of the train. Thereby, the existence of a train in the section can be detected.
In detecting the existence of a train, a high reliability is required, because a control device on the ground (a wayside controller) utilizes a train detecting signal generated as described above to locate the train and to operate traffic signals for the train. Particularly, for the purpose of securing adequate safety in the train service, it is absolutely essential to avoid possibility that, although a train actually exists within a certain section forming a track circuit and therefore the pair of rails which form the track are short-circuited, a signal indicating no train in the section of the track circuit is erroneously transmitted, possibly due to a failure in a transmitter/receiver device, for example.
Conventionally, to solve such a problem, highly reliable equipment has been used for the transmitter/receiver devices installed in every track circuit, as well as for the wayside controller. When any trouble occurs in transmitting or receiving signals, the control which is carried out is as follows: i.e., no signal is transmitted on the transmitting side, and a determination is then made as to whether no signal is received on the receiving side.
In the conventional system as mentioned above, the large number of transmitter/receiver devices must be subject to very careful maintenance. Further, an individual signal cable is used for the connection between every transmitter/receiver device and the wayside controller, in order to avoid possible misrecognition of information among the devices.
Furthermore, JP-A 6-92232 proposes that a signal, which has a different frequency for every track circuit, be used in order to avoid erroneously receiving a train detecting signal from an adjacent track circuit.
To sum up, as described above, when any trouble occurs in transmitting or receiving, the conventional system carries out control in such a manner that, if trouble occurs on the transmitting side, no signal is transmitted, and if it occurs on the receiving side, it is judged that no signal is received. To this end, highly reliable devices must be utilized for a transmitter/receiver device. As a result, the transmitter/receiver device has become complicated in its structure and therefore can not be made small in size.
Since such a device is needed for every track circuit, the total system becomes extremely high in cost. Further, in order for a transmitter/receiver device to achieve the above mentioned control, it must be sufficiently maintained and inspected. Such maintenance and inspection work is very troublesome, since the work must be done for every one of a large number of devices arranged along a wayside.
Further, while the technology disclosed in JP-A-6-92232 might have the effect to avoid erroneously receiving a train detecting signal from an adjacent track circuit, it cannot solve the problem of being high in cost, due to its complicated system construction, which is needed for maintaining the reliability of a transmitter/receiver device, nor the problem of being very troublesome in the amount of maintenance and inspection work required to assure proper operation thereof.
An object of the present invention is to provide a train detection system of simple construction for detecting the existence of a train and which is easily operable on a fail-safe basis when trouble occurs in transmitting or receiving a signal indicating the existence of a train in a track circuit section.
Further, another object of the present invention is to provide a train detection system which can easily detect a failure in a signal transmission path with a simple structure.
The above mentioned objects can be attained by a train detection system comprising a transmitter for transmitting a train detecting signal to a track circuit, a receiver for receiving the train detecting signal from the track circuit, and a wayside controller connected to the transmitter and the receiver through a data transmission path for supplying the train detecting signal to the transmitter and receiving the train detecting signal from the receiver to detect the existence of a train, wherein the transmitter comprises a unique code memory for storing first unique code data and for adding the first unique code data to the train detecting signal received from the wayside controller, which signal is then transmitted to the track circuit, wherein the receiver comprises a unique code memory for storing second unique code data and for adding the second unique code data to the train detecting signal with the first unique code data received from the track circuit, which signal is then transmitted to the wayside controller, and wherein the wayside controller comprises unique code checking means for checking whether or not the first unique code data and the second unique code data received from the receiver agree with the contents of predetermined stored data.
With the above mentioned construction, even if any failure occurs in a transmitter or a receiver and the receiver erroneously produces a detecting signal indicating no existence of a train to a wayside controller, the controller judges the possibility of the train existence and can perform safe control, because the detecting signal does not include the required unique code data or, if included, the included unique code data is not correct.
If any failure occurs in another portion of the transmission path, the failure can be detected in a similar way. Further, if the receiver erroneously receives a signal from an adjacent track circuit, which is transmitted to the wayside controller, the controller can judge that it is an error signal.
According to the above mentioned construction, if only a wayside controller for checking the unique codes is constructed with a very high reliability, a transmitter/receiver device to be provided for every track circuit can be made with a simple structure, which can reduce the cost of the total system (only one wayside controller is required for a lot of track circuits).
Further, if the wayside controller is highly reliable, there occurs no serious problem, even if the transmitter/receiver device itself provided in every track circuit has a relatively low reliability. Therefore, it is possible to simplify the maintenance and inspection work of many transmitter/receiver devices arranged along a railway.